Structure formation and mechanical properties of thermoplastic elastomer and oil system having a microcellular porous structure

A novel microcellular porous structure, the product of a small proportion of a semicrystalline thermoplastic elastomer and a large proportion of low molecular weight oil, was examined. The system exhibited a unique three‐dimensional continuous polymer network, consisting of interconnected spherical cells of a few tens of micrometers in diameter. In this report, details of morphology and stress–strain relationship of the system, which is made from hydrogenated poly[butadiene‐ b ‐(styrene‐ random ‐butadiene)] (H‐SBR) as a semicrystalline thermoplastic elastomer and straight asphalt as an oil, were investigated and analyzed. The system exhibited inverse S‐shape type stress–strain curves, but was characterized by extension rate and polymer concentration dependency. It was demonstrated that the stress–strain curves of the system can be described by a simple combination of that of two phases: asphalt‐rich phase and H‐SBR–rich phase. Calculations of a simple parallel model quantitatively agreed with experimental data, especially in the case of higher polymer concentrations (about 12 to 20 vol %) where uniform polymer network is formed over the whole system. Disagreement between calculation and experimental data was, however, found in the cases of very small proportions of H‐SBR (< ∼ 8 vol %), where the polymer network structure in the system was imperfect. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 107–112, 2005